Hi all - so after nearly two years owning my ff I am contemplating getting a 4.2 s/c ff next around 2008. It will be next year now and just thinking but a few questions ideally from people with experience of both...

What gets better mpg? The book reckons the 4.2??? Is this due to gearing? It will be on runs a fair bit.

Reliability- lpg aside what’s the more reliable engine and what about the same question at 120k plus?

Cost of running overall ? Guessing pretty similar?

Cheers! Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

I have the 4.4 and I only have the amount of threads I read about problems as experience and so I would say the SC is both more reliable and more efficient having the supercharger.
The 4.4 is an old BMW M62 engine dating back to the 90’s in one form or another but saying that it isn’t a bad lump if maintained and can get to 200k miles.
I think any engine can be bad if not looked after.

In terms of running costs, they're not wildly different. The AJV8 is a bit more modern, and probably the best engine fitted to any RR in terms of reliability against performance.
The real difference is performance. The SC is streets ahead of the M62.

Does the 4.2 have the same chocolate gearbox as the td6?

No it has the later mych improved 6 speed

No it has the later much improved 6 speed

No, it has the ZF 6HP26 which is a 6-speed box which seems pretty good if you ignore JLR's "sealed for life" bull about the transmission oil. 2006MY 4.2 SC
BMW R1250 GSA Rallye TE
Triumph Tiger 1050 (sold)
1979 Pontiac Trans Am (sold)

The gearbox is fine the solenoids can be temperamental but most issued solved by changing fluid - I change mine every 30 to 40k

great thanks guys - now i will ask the dreaded question - are they that much worse on leg in terms of reliability? Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

also - a little earlier than I'm looking but do the 2005 models still use any of the bmw components like bus or anything as the interior is pretty much the same? Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

To give you an idea I have a couple of Range Rovers and my 4.2 I bout 4 years ago on just short of 80k miles it has now done nearly 165k in that time I have changed front struts and when I did that i changed the pump my choice but I tend to do preventative maintenance I have changed the water pump and all pulleys and belts last year as they were 10 years ol same with the battery to starter lead all working but could be an issue - I also replaced all bushes and ball joints at 125k - still drives like a dream - I do quite a few long runs to south of france so don't want any grief - it has never let me down I will change all the heat exchanger rads next year so in a nutshell fabulously reliable if you look after them and service them as per the schedule or more ignore bits and it will bite you - I also believe the one that are used daily and do miles are in much better condition that those left to do 30 miles a week

The SC gearbox is much better than the TD6 unit, but can still suffer premature failure if not maintained. Mine failed at 96k. As others have said, ignore the LR service schedule for the gearbox, and replace oil and filter every 30-40k.

I believe all the SCs had the updated bus, but all FFRRs use some BMW bits.

Plenty of SCs have done massive mileage, if looked after.

Many people don't like LPG on the AJV8 as there are stories of valve seat recession, but equally, there are plenty about that have been converted, usually with valve oilers, and have done plenty of mileage without problems.

If i was buying a petrol one today i would opt for 5.0 SC, 4.2 SC and then the 4.4( don't tell my fatty tho)

My 4.2 SC is now on 207k miles! Gearbox was rebuild by a previous owner and then I got the solanoids sorted as the rebuild hadn't fixed it. Ive owned it for almost 3 years and it's had front struts, radiator, water pump, air con pump. But most of that is just age / mileage related as not specific to the SC spec.